I think it would fall under just plain ordinary construction rules. It's a building. All the showers &c are indoors? Even with a lot of gaps at the tops of the walls, it's still indoors.
What kind of water heaters? Gas? Electric? How many?
Throne, Sink, and Shower? No bathtubs, I hope!
What's the layout like? Central hall with doors to the individual bathrooms? No common shower area? In that case, I'd run as much as you can through the central hall, with J-boxes branching off to each bathroom. You could keep the central hallway as a 'dry' location, but you'd be much better off classing the entire building as 'wet.'
I'd call the bathrooms 'wet,' so almost everything better be waterproof! Yes, it'll -all- get wet. Get a Troop of Boy Scouts having a splash party, and it better be water proof!
And there will come a time when you find a bathroom completely trashed, such that just opening the door takes an act of will. You will want to take a hose with hot water and just spray down the entire room, and try to get whatever is on the floor down a drain without touching it!
Oh-- drains-- one in the bathroom (on the floor) in the shower area, another just for luck. At least 1 or 2 in the common area.
Hmm.. I've been assuming this hasn't been built yet! Is it?